\begin{table}%t2
\caption{Reactions from \cite{horn04a}, with adjusted rates$^{a}$.}
\label{tab2}
\small%\begin{center}
{
\begin{tabular}{l c c c}
\hline\hline
Reaction & $k(300$ K$)$        & $T$-dependence, $\alpha$ & $k(10$ K$)$          \\
         & (cm$^3$ s$^{-1}$) &                        & (cm$^3$ s$^{-1}$)  \\
\hline
 & & & \\[-8pt]
 (4) CH$_3$OH$_{2}^{+}$ + H$_2$CO $\rightarrow$ CH$_3$OH$_2$OCH$_{2}^{+}$ + $h \nu$ &  $3.1 \times 10^{-15}$  
&  --3    &  $8.4 \times 10^{-11}$ \\
 (5) H$_2$COH$^+$ + H$_2$CO $\rightarrow$ H$_2$COHOCH$_{2}^{+}$ + $h \nu$ &  $8.1 \times 10^{-15}$  
&  --3    &  $2.2 \times 10^{-10}$ \\
 (6) CH$_{3}^{+}$ + HCOOH $\rightarrow$ HC(OH)OCH$_3^{+}$ + $h \nu$ &  $1.0 \times 10^{-11}$  
&  --1.5  &  $1.6 \times 10^{-9}$ \\
\hline
\end{tabular}}

{
$^{a}$ $k(T) = k(300$ K$) \times (T/300)^{\alpha}$.}
%\end{center}
\par
\end{table}